Device for regulating the air volume flow for a vent in a laboratory

ABSTRACT

A device for regulating the air volume flow for a laboratory exhaust, has a rectangular housing ( 6 ) which can be arranged on the laboratory exhaust. The device is equipped with inflow devices that can be connected to the interior of the laboratory exhaust and with outflow devices ( 8, 12, 13 ) that can be connected to an exhaust air system. The interior of housing ( 6 ) is divided by a partition ( 17 ) into two parts, namely a calming part on the exhaust side and a measurement and regulating part on the outflow side, and these two parts are connected by an air deflection area ( 18 ). A rectangular measurement orifice ( 20, 25 ) has pressure measurement devices ( 22, 23, 24, 28, 29 ) and a rectangular regulating flap ( 21 ) arranged one after the other at a distance in the direction of flow between a housing wall and the partition ( 17 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a device for regulating the air volume flowfor a laboratory exhaust.

2. Description of Related Art

Laboratory exhaust systems must comply precisely with the volume flowlimits stipulated by legislation. However, because of the spaceconditions, it is almost impossible to accurately measure and displaythe air volume flow, because the flow conditions in front of and insidethe exhaust are disturbed, and due to the structural situation, there ishardly any space to include, a usable measurement zone afterinstallation of an exhaust. Therefore, when using an exhaust system,measurement and regulation of the air volume flow stipulated bylegislation are very problematical.

German Patent Application 19528780 A1 has already described ameasurement device for measuring the air volume flow through an exhaustby means of which the amount of air flow rate can be measured with avery high precision. This measurement device includes a housing, whichcan be placed on the exhaust and is equipped with inflow devices thatcan be connected to the interior of the exhaust and outflow devices thatcan be connected to an exhaust air system. The interior of the housingis subdivided by a partition into a part on the exhaust side and a parton the outflow side, the two parts being connected by an air deflectionarea. A pipeline is provided in the part of the interior of the housingon the outflow side, with a measurement orifice being arranged thereinfor measuring the air volume flow.

This known device is used exclusively for measuring the air volume flow,but there is no possibility of regulating the air volume flow. The airflow is deflected repeatedly inside the housing, namely from the part onthe exhaust side into the part on the outflow side and from there intothe pipeline and from the pipeline back into the outflow channel, thusresulting in a very great pressure drop.

German Patent Application 19545948 A1 describes a device for measuringand regulating the air volume flow in an exhaust, but it has thedisadvantage that a calming zone is needed upstream from the regulatorof this device, and this makes the device bulky.

German Patent 196 00291 A1 describes a device for measuring the pressuredifference in a gas flow in which it is possible to switch between twodifferent measurement methods by way of comparative measurements, sothat the measurement methods can provide mutual monitoring in this way.However, there is a switch here between measuring a static pressure andmeasuring an effective pressure, which has the disadvantage thatmeasurement of the static pressure depends on the installation site ofthe exhaust, the position of the sliding window and similar parameters.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide a device forregulating the air volume flow for a laboratory exhaust system which iscapable of not only measuring and monitoring but also regulating the airvolume flow independently of the type of exhaust and the oncoming flowand outgoing flow arrangements involving the exhaust.

Another object of the present invention is to make it possible tomeasure and regulate the air flow rate through the exhaust over theshortest possible distance.

A further object of the present invention to provide a device forregulating the air volume flow for a laboratory exhaust system that iscapable of monitoring the air volume flow independently of theinstallation site and location of the laboratory exhaust system byintroducing another measurement site for the air volume flow.

These objects are achieved by providing a device for regulating the airflow volume flow for a laboratory exhaust system having a rectangularhousing which can be placed on the laboratory exhaust. The device isequipped with in flow devices that can be connected to the interior ofthe laboratory exhaust and with outflow devices that can be connected toan exhaust air system. The interior of the housing is divided by apartition into two parts, namely, a calming part on the exhaust side anda measurement and regulating part on the outflow side, these parts beingconnected by an air deflection area. Also provided is at least onerectangular measurement orifice having pressure measurement devices anda rectangular flap arranged one after the other in the direction of flowbetween the a housing wall and the partition in the measurement andregulating part with a distance between them.

In one embodiment, two measurement orifices are provided, these beingarranged at the same level in the measurement and regulating part in thedirection of flow.

In another embodiment, the pressure measurement devices are designed sothat they detect the effective pressure in front of the at least onemeasurement orifice, downstream from the at least one measurementorifice and downstream from the regulating flap and they form theeffective pressure differences across the regulating flap.

In yet an other embodiment, the device includes a sound-absorbent liningin the housing.

In a further embodiment, at least one measurement orifice and aregulating flap are arranged in such a way that calming zones are formedbetween the deflecting area and the at least one measurement orifice andbetween the at least one measurement orifice and the regulating flap.

In another embodiment, the device includes a maintenance port designedin the front side of the housing.

In another embodiment, the depth of the housing is greater than itsheight.

These and further objects, features and advantages of the presentinvention will become apparent from the following description when takenin connection with the accompanying drawings which, for purposes ofillustration only, show a single embodiment in accordance with thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an exhaust with the embodiment of the deviceaccording to this invention;

FIG. 2 is a cross-sectional view of the exhaust illustrated in FIG. 1;

FIG. 3 is a cross-sectional view of the embodiment of the deviceaccording to this invention;

FIG. 4 is a front view of the embodiment shown in FIG. 3; and

FIG. 5 is a cross-sectional view of the embodiment of the deviceaccording to this invention, shown in greater detail.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIGS. 1 and 2, a conventional laboratory exhaust 1 has asliding window 4 through whose gap air flows into the interior space ofthe laboratory exhaust 1. This air usually flows through various slots 5from the working space of the laboratory exhaust 1 into an intermediatecollecting space or a reduced pressure chamber 3 in the interior of thelaboratory exhaust 1.

A device for regulating the air volume flow which flows through thelaboratory exhaust 1 sits on laboratory exhaust 1. This device includesa rectangular box-shaped housing 6, which is connected by one or moreconnection points 7 to the reduced pressure chamber 3 of the laboratoryexhaust 1. Depending on the type of design of the laboratory exhaust 1,the connection points 7 may be one or more pipes or slotted connectionchannels. The device is also equipped with air deflection devices and anoutflow channel 8 through which the air flows out of the device and intoan exhaust air system at the installation site and is dissipated.

The inflow devices of housing 6 may have various designs, depending onthe design of the laboratory exhaust 1. A laboratory exhaust is oftenequipped with a round pipe piece 9, as shown in FIG. 5, which may beconnected directly to the housing 6. Other laboratory exhausts have twoconnections 10 and 11, which can be inserted into the housing 6 likepipe piece 9. It is also possible to provide rectangular slots in thehousing 6 instead of round openings.

The housing 6 is usually equipped with a round connection piece as theoutflow device 8 through which the housing 6 can be ventilated. However,this connection piece may also be rectangular in shape. If necessary,the outflow device may also be installed at another location, i.e., itmay lead out of the housing 6 not from above but instead to the right.In this case, a rectangular outgoing connection piece 13 is provided, asshown in FIG. 5. It is also possible to provide an outlet leading out ofthe housing 6 to the front through a rectangular connection piece 14 or15 or to the rear. Therefore, the device may be equipped with variousinflow devices to adapt it to specific laboratory exhaust systems and sothat it can also be ventilated in various ways, namely upward, to thefront, to the right or to the rear.

As shown in FIGS. 3 and 4 and in particular in FIG. 5, the box-shapedhousing 6 is divided by a single partition 17 into two parts, namely anintake and calming chamber 16 and an upper chamber 19, these chambersbeing connected by an air deflection area 18.

A rectangular measurement orifice 20 is provided in the upper chamber19; it is arranged between the partition 17 and the inside surface ofthe upper wall of the housing 6 and consists of a rectangular component.The air volume flow is measured at this measurement orifice 20.Downstream from the measurement orifice 20, a rectangular regulatingflap 21 for regulating the air volume flow is provided in the upperchamber 19. This rectangular regulating flap is also mounted between theinside surface of the upper wall of the housing 6 and the partition 17.A pressure sensor 29 is situated so that it measures the effectivepressure 28 upstream from the measurement orifice 21 and the effectivepressure 22 downstream from the measurement orifice 21, forming fromthis the effective pressure difference across the measurement orifice20. The air volume flow can be determined accurately from this.

In an especially preferred embodiment which is shown in FIG. 5, theeffective pressure downstream from the regulating valve 21, i.e., at alocation 23 is also measured. An effective pressure 24 can be formedfrom the combination of the effective pressures 22, 23. This combinedmeasurement of effective pressure differences at measurement sitessituated in succession in the flow channel allows a determination of theair volume flow over a much broader measurement range.

As also shown in FIG. 5, the design may be such that another measurementorifice 25 is provided at the same height in the direction of flow, anda neutral measurement is performed at locations 26 and 27, e.g., withthe help of tubing connected there, so that the air volume flow of theexhaust is determined and checked independently of the oncoming andoutgoing flow conditions.

An adjusting drive may be provided for actuating the regulating flap 21on the device.

The regulating device may be connected to sensors (not shown) that aremounted on the sliding windows 31 of the exhaust.

By means of the device described above, it is possible to measure theair volume flow, i.e., the air flow rate, and to regulate it at aconstant level or to vary it by way of the sensors on the slidingwindows 31 illustrated in FIG. 1 as a function of the position of thesliding windows. The additional measurement site 25 is used formonitoring the regulating process. This can be checked by known methodsaccording to German Patent Application 19600299 A1; however, thefunctioning of the device can be checked at any time through themeasurement at the additional measurement point 25.

The device is designed so that it takes up most of the width of theexhaust. Therefore, it can be placed directly on the laboratory exhaust1 without requiring any additional air collecting channels. The requiredair collecting channels are integrated into the device.

With such a width of the device, the path 32 between the deflecting edgeon the partition 17 and the measurement orifice 20 is so long that anadequate oncoming flow at the measurement orifice 20 and/or measurementorifices 20, 25 can be achieved. If the path between the measurementorifice 20 and the regulating flap 21 is long enough, this results inexcellent oncoming flow distances, and measured values with a highaccuracy can be obtained. An inspection port through which themeasurement sites of the pressure sensors and the regulating valve canbe monitored at any time is provided in the front area 34 of the device.

This device does not have any direct sound emission into the interior ofthe laboratory exhaust, because the air is deflected. Therefore, thedevice also functions as insertion damping with a sound attenuatingeffect.

However, if the sound level is to be further reduced, it is alsopossible to line the inside walls of the housing 6 with sound absorbingmats 35, 36, shown in FIG. 3.

1. A device for regulating the air volume flow for a laboratory exhaust,comprising: a rectangular housing equipped with inflow devices that areconnectable to the interior of the laboratory exhaust and with outflowdevices that are connectable to an exhaust air system, the interior ofsaid housing being divided by a partition into a calming part on anexhaust side and a measurement and regulating part on an outflow side,said calming part and said measuring and regulating part being connectedby an air deflection area; and at least one rectangular measurementorifice having a plurality of pressure measurement devices and arectangular regulating flap consecutively arranged with a distancebetween said at least one rectangular measurement orifice and saidregulating flap in a direction of flow between a housing wall and saidpartition in the measurement and regulating part.
 2. The deviceaccording to claim 1, further comprising two measurement orifices, saidmeasurement orifices being arranged at the same level in the measurementand regulating part in the direction of flow.
 3. The device according toclaim 2, wherein the plurality of pressure measurement devices aredesigned to detect an effective pressure in front of the at least onemeasurement orifice downstream from the at least one measurement orificeand downstream from the regulating flap, and to form the effectivepressure difference across the regulating flap.
 4. The device accordingto claim 3, wherein the plurality of pressure measurement devices areadapted to detect the effective pressure in front of the at least onemeasurement orifice downstream from the at least one measurement orificeand downstream from the regulating flap and to form the effectivepressure difference across the regulating flap.
 5. The device accordingto claim 4, wherein said housing contains a sound-absorbent lining. 6.The device as recited in claim 5, wherein the at least one measurementorifice and a regulating flap are arranged to form calming zones betweenthe deflecting area and the at least one measurement orifice and betweenthe at least one measurement orifice and the regulating flap.
 7. Thedevice according to claim 6, further comprising a maintenance port in afront side of the housing.
 8. The device according to claim 7, whereinsaid housing has a depth that is greater than the height of saidhousing.
 9. The device according to claim 8, wherein the plurality ofpressure measurement devices are adapted to detect the effectivepressure in front of the at least one measurement orifice downstreamfrom the at least one measurement orifice and downstream from theregulating flap, and to form the effective pressure differences acrossthe regulating flap.
 10. The device according to claim 1, wherein theplurality of pressure measurement devices are adapted to detect theeffective pressure in front of the at least one measurement orifice,downstream from the at least one measurement orifice and downstream fromthe regulating flap, and to form the effective pressure differencesacross the regulating flap.
 11. The device according to claim 1, whereinsaid housing contains a sound-absorbent lining.
 12. The device asrecited in claim 1, wherein the at least one measurement orifice and aregulating flap are arranged to form calming zones between thedeflecting area and the at least one measurement orifice and between theat least one measurement orifice and the regulating flap.
 13. The deviceaccording to claim 1, further comprising a maintenance port in a frontside of the housing.
 14. The device according to claim 1, wherein saidhousing has a depth that is greater than the height of said housing.